Instrument for automatic, integrating radiation measurements



p 28, 1954 H. P. HOVNANIAN 2,690,076

INSTRUMENT F( )R AUTOMATIC,- INTEGRATING RADIATION MEASUREMENTS FiledJan. 16, 1.950 2 Sheets-Sheet 1 Inventor Hrair P. Holman/an it w 9 74 w.t

P 1954 H. P. HOVNANIAN ,0

INSTRUMENT FOR AUTOMATIC, INTEGRATING RADIATION MEASUREMENTS Filed Jan.16, 1950 2 Shets-Sheet 2 Inventor Hra/r P. Hovnanian WWW; Em

Patented Sept. 28, 1954 INSTRUMENTFOItAUTOMATIQINIEQRAT INGRADIAT-IONMEASUREMENTS HrairP. Hovnanian, Winchester, Mass; 1 Application January#16, 1950, serial'Noij-lssiss i 8 Claims.

This; inventionrrelates :to radiation measuring: instruments and. more:particularly -to' photo metric instruments .ofzthez integrating type andit has for its primary obj ect to provide an :m--: stnumentfor measuringradiant. power and/or ene-rgy,;suchas for instance :the power and/ orenergy" of-light per unit area lwhich instrument operates fullyautomatically and continuously and with a precision which'is muchhigherth'an that; obtainable with other instruments 'ofthiscomparatively: extended period- =in order to produce a highdegree-ofprecision, while the latter metho'd'can only becarried into effect bymeans of (a defiectionalinstrument; such asagalvanometer,:the-precisionof which depends on the constancy :ofmagnets, ispringsg bearings and on r the level: of the instrument: i Thedegree of pre cision: obtainableiabyumeans of the first Enamedmethodtherefore clearly depends on the skill o'f then-operator,'rwhilei the 'sprecisionof the latter-c method depends-on many" factors,such as temperature; age and vibrationnafie'cting the precision to avarying degree-'1'ln both cases'however, a highly-trained or skilledobserveris essential and indispensable.

Electricrmeasurements. of radiation-are more over mostly'carried out. bymeans=of a" photo-cel1-' arrangement, the current generated in thephotocell drivingthe :measuringrinstrume'nt? As these 1 currents; areweakponly instrument readings can be produced; :but an'automatic'recording of sumcientprecision :is not obtainable.

According to ithe' invention the above drawl backs: and-; disadvantagesof :the known A methods" are? eliminatedaand' a: fully automaticintegrating operation is obtained a by :measuring the power or energy:of theradiation by Pmeans of a pair of thermocouples one of which. hasits junction ex-" posed-- to the radiationto be measured while I theother: ends are kept: at thesame temperature at which similartnends ofthef'second"thermocouple" are; kept-m the "secondz. thermocouple isheated by a current finely con-trolled by the the'rmocurrent jointlyproducedaby ithe pair, which heatin'g'cur rentzaiscut: off :when-ztheLtherimocurrents producedin thestwoz thermocouplesiof the pairopposeeach supplied electric ipowe'r or 3 energy 1 i'nece's's tiOIi'il'iWhi'Qha recordin 2 other and furnish a difie'reiid'e' which "is equal?to m1... Thel mumntpwen and/0r 'ene'r 'g'y of' 1;. cf radiationimpinging upon the firstthermocb mj can thus be measured by measuringthelooally' heat the second ooii'ple to the pom at which"the" difierenceis 1 nil 'and' th'e" heating ourre'nt is out Off;

As-Zth meas'ii-re'd '1ocal nergy sup ly is entirely regulated by'theapparatus itself'e'nd by the bal an'cing' ofthe currents produced by"the ftwof thermocouples it 1 is "an" exact 'eqiiivalnt" -'totheenergySupplied by th radiatiori obtained 'in' a fully automatid recess." The*opeiatbr needf l therefore 'notread the instrflinnt afte'r thef-initial adjus'tnfer'it' if a recording instrument is used in the"circuit;-' y p The aboi/e--"des"i ibed" operatiofl'wo'uld be per'f jfectly accurate and 'xact i'f the decre'a's"in the voltage of thethermocurrent andtheincre'ase and decrease of the' ontrolled-"localheating gui rent would occur at the sams mfiemtes' Thisf'i's howevernot'theaseanda direct control of 'the heating current in absoluteproportionalityto the voltag'eldeveloped by the manne uin-couples cantherefore "not" be'-'"obtaind with' -simp1e means; such askn'ownf wherehigh-precision is required f Accordi'r'igto the -invention a sufficientapp'r'oizi matio'rr deiiiatih'g 'from the 'thbretic'al -value only to*anexte'ntwhich "may be made as'sma'll as de sired'j'can" be'obtairid-by a -'control exercised either by"me'an sof relay-switches orby means of "anele'ctranictube dpemnng with a trigger ac tio'nu andthereby switching the heating current on and o'ff so "as to"fond-shortimpulses as long as the differential thrn'iovoltage hasa predetermined'*'sm'a1lvalues Theoretical fconsideratio'ns' then show that inthis case, when only short timed impulsesare used*th approximatio issufiioient- 1y Close for measurements giving thhighest pre cisioni' h Itis thus' 'sefi-thatit one of the" eneral 0b'-" jects'of 'theinventioi'rto obtain 'a' fully automatic' operation (if 't'ln'e instrument so thatpractically" no a'ctiifityof 'an ob erver is necessary during the"recording-of the v'aluesto bemeasur'ed.

It is 'also s'ee'nthat" it is a fur'ther'object' of the invention toproi/idea high firecisio'r'iphotometrie instru'mhflforth iibwe'rbrehig'y"6f the radia te'r may-continuously register'thevalues-whith-nbeenmasured."

It is a still further objector the invention 'td' provide ameasunrig'mstrumem involving a tri er-"acuom b meansofwhieh"thermdeurrents" produced in a pair-6f thermooouplsftine couple ofwhich is exposed to a radiation, while the other is exposed to locallygenerated heat, may control the heating current furnishing the locallygenerated heat automatically to such an extent that the power or energysupplied by it to one thermocouple is exactly equal or proportional tothe power or energy to be measured, the electrical power producing thelocally generated heat being supplied by a series of impulses of shortduration.

It is a still further object of the invention to provide means forcarrying into effect the measurement of radiation, which includes adevice operated by trigger action, the said action being exercised bythermocurrents opposing each other and generated by a thermocoupleexposed to the radiant energy to be measured and by a couple exposed toa local heating means, said local heating means being heated by a seriesof impulses of short duration, automatically supplied by the triggeraction device, said impulses continuing as long as the differencebetween the thermocurrents generated by the radiation to be measured andby the locally produced heat has not disappeared.

Further and more specific objects will be apparent form the followingdetailed specification.

The invention is illustrated in the accompanying drawings, showingseveral embodiments of the invention and modifications thereof. It ishowever to be understood that the diagrams illustrating the inventiononly show examples by means of which the principle of the invention andthe best modes of applying said principle may be explained. Thediagrammatic examples will not give a survey over all the apparatus ordevices which may be used in connection with the invention andmodifications of the arrangements are therefore not necessarilydepartures from the essence of the invention.

In the drawings:

Figure 1 is a diagram illustrating one embodiment of the invention.

Figure 2 is a diagram illustrating another modification of theinvention.

As has been briefly stated above radiation measurements by means of theinstrument according to the invention are based on the generation of acurrent by thermoelectricity caused by the impinging of the radiationupon a thermocouple, the said radiation producing a raising of thetemperature at the fused ends or hot junction of the thermocouple so asto generate a thermocurrent. An exactly similar thermocouple isconnected in opposition to the first named thermocouple, the cold endsof both thermocouples being connected and exposed to the sametemperature. However, the hot junction of the said second thermocoupleis exposed to the heat radiating from or transmitted by an electricheater. The common leads of the two thermocouples connected inopposition carry a current controlling a local heating current for theaforesaid electric heater produced by a local source. As this controlmay be exercised with high precision the current supplied to the heaterwill be practically cut off in the moment in which the hot junction ofthe second thermocouple, exposed to the local heater, reaches atemperature which is equal to that of the first thermocouple and thewattage necessary to produce said heating is thus directly related tothe radiant energy impinging on the first named thermocouple.

The methods of controlling the local heating current by means of the twoopposing thermocurrents may vary considerably.

For high precision instruments attention has to be paid to the fact thatthe increase and decrease of the controlling currents and of thecontrolled currents occurs at different time rates and that thereforedirectly operating arrangements, while being fully automatic, would showa certain lack of precision. To obviate this de fect it is preferable touse devices having a certain trigger action and, where high precision isrequired, to eliminate as far as possible the eifect of the differenttime rates at which the currents vary by supplying the local heatingenergy in the form of short timed impulses continuing for a period oftime which is determined by the trigger action of the thermocurrents. Onaccount of the short duration of the local impulses the time rate atwhich the energy is delivered is not material.

Care however has to be taken to produce these impulses automatically.This is preferably obtained by an arrangement in which the heatingenergy is furnished by a condenser discharge, which is constantlyinterrupted by a relay operated by the discharge itself, so that thecondenser will have time to recharge and will thus deliver impulseswhich are practically all of the same duration, power, and wattage. Itis thus possible to obtain as close an approximation to absoluteproportionality between the controlling thermocurrent difference and thecontrolled heating current as is desired.

The examples shown will clearly illustrate the above explainedprinciples.

A thermocouple 5, hereinafter termed radiation receiving thermocouple isso arranged that the junction 6 at which the wires are fused and whichis usually termed the hot junction rests on the radiation receivingplate 7 which is heated by the radiation to be measured, for instance bythe light of the sun, if the instrument is used as a pyroheliometer. Thecold ends 8, 9 which may be held at a definite temperature, for instanceat 32 F. by means not shown, are connected or in contact with the coldends 8a. 9a, of an exactly similar thermocouple Iii, hereinafter termedthe compensating thermocouple. The hot junction [2 of the saidthermocouple l5] rests on a cold plate i I similar to the radiationreceiving plate 1, which is however provided with an electric heater l5.The plate It and the hot junction I2 of the thermocouple Hi has ofcourse to be protected against radiation.

The thermocouples may be of any approved type, for instance of the typeusing an alloy of Bi-Sn against an alloy of Bi-Sb. A couple of this typefurnishes a yield of 120.10 volts per degree 0.

As seen in Figure 1 the cold ends 8, 8a, 9, 9a of both thermocouples 5,H) are connected with conductors l5, I? which lead to the D. C.amplifier 18 which may be of any usual or approved electronic type andwhich need not be described. One of the many amplifying arrangementswhich may be used is described by H. Tatel and others in the Review ofScientific Instruments, vol. 9, No. '7, 1948. Another of thesearrangements is described by Vance, ibid., vol. '7, No. 12, page 489,1936.

The D. C. amplifier cooperates with a. thyratron 2!) which, as wellknown, is a tube with a trigger action, controlled by impulses exceedinga definite predetermined value. Moreover this tube can controlrelatively large amounts of power with a small input power. Thethyratron 2%) is operated in this case by the output voltage of theamplifier which is substantially proportional to acemom ethe-:difierencexof the-thermal:woltageseproducedms by the=-thermocoup1es;r:-.

The plate: circuitv 26 of thesthyratronuncludes (it a relays-2iand-resistances 1'-2 2,;.-23. :";;The..-.rela y:7;| a: controls at itscontact 24 a localacircuite25 pow-m6 ered by theicondenser 35 and:connected Wit/'11: a.- local battery: 32' which-may be identical with:the E' F plateacircuitibattery of the thyratron; ..-.This circurt-r25also includes-1 the .cold @platevheater-irew r7" sistance i5. 10

Across =the.'circuit- 25 thes recordi-ngmeterfin is connected .-:bymeans .i of mwhichLathe pharosage g (radiant power permunit area)...orthe. phosagecp (radiant energy pen unitrarea) maysibe ldirectlyancLaccurately recorded. 7. Moreover, the; circuit .15 includeslrelaw.33 controlling i the 2. contacts 134 l which! control theplate-cathodecircuit 26 n 6f theithyratro'n.

Wli'enthe radiation receivin'g'thermocouple 6 is t. heated by:the"radiation' to bemeasured;the "cold" plate and the compensatingthermocouple H! be ing'cold in this phase of the operationyathermo icurrentis' flowing through'the' conductors 16, H and'a' voltage built upbetween' the' points-Wand 9 whichis a-mplified'in theamplifier' 4 8."-The"*' amplified --voltage now acts on the "grid-" 9 of thethy'r'atro'n-M which is non-conductingin its r'rormail' state. a" If asuflicientwoltage' has'f been buil up in the amplifier the thyr'atronbecomes conductive snddenly so thatta surge' 'o'f current 'wvil flowthrough the .plate circuit't218 of the thyr'atron'. The? 'currentfrsurgerpassesi mela-ynZ-l ewhich TGIOSBSIS- contact 2'4,wthus closing a".dischargergcircuitxfor the Econdenser which-includes :the circuit :2 5,I 1/ thescold plate heater l5 and-thetrelay 3,3. "The,r3 meter 30 isconnected1=across-.-the.-circuits- If relay-33 wouldnotbe inthe-.circuit thethyewratron would continue to function:-=and=-the:cur-.- rentwould. flow through the :heatercontinuouslyx; 1 as:long as the voltagecin theaamplifierei-s above- F thew-operatingvalueof the :igridwvoltageeof ith thyratron. -=-Therefore:-.theheatertwouldebe supt pliedtwith "heat-energy at a-decreasing mateafromthe condenser and at a constant rate from:.the2-;-1- battery :32 Thecold:piate\ :H wou-ldbe -heated to and beyond the temperature requiredfor-tproduci-ng a compensatingor neutralizingscurrentrin 1 couplertfl onaccount of the different :time =rates-i at which the i thermocurrentsand ri'iheiiheater a: currents .decreaseand increase -respectively. The1-50 accuracy of the measurement this :casewvould: a not be very high;

The relay 3.3 howeveryopera-tesimmediatelyup on the-discharge of theicondenser as it is in the discharge: circuit-w It :cuts-r outwthethyratrom-esmakes: the relay r21 fall :baclc .and therefore also-w:interrupts therheating.-circuit .'a The duration-and 1-;- also theenergy of a-single impulse isthus limited andris aconstant factorLnIfonesi-mpulse .is suffi cientito heat the :resistance:l5 to the requiredex tentgaimparting -."to the acompensating: ;thermo.- couplema'itemperatu're-equal to'thatzto-which the radiation i receiving 1thermocouple 6 has -been' heated,-the operation ceases and the wattagefurnishe'd by theheating current-is recorded'on the recording meter. I I

If the temperature of the hotiun'ctionfi of the couple- I E: does notreach "therequiredi'value; the operation-is repeated, successiveimpulses are sent and recorded u ntil the'des'iredlresult is accom-r-nplished .andwthethyratronoperation is out ofi-by H. theLgrid l 9 being.no longer-provided With finbifia$=wfing wvoltage permitting thedischarge eof uthe a. tube-20. 76

The dxetrtingmf the heateriresistancezi 5 by i-me pulses eliminates theinfluence of thedifierentiw,

timeratesof therthermocurrent increaseand.'-decrease; of rthescondenser.discharge-gand-of the.

the ti-merates-;therefiore-becomes negligible; The duration of theimpulsesis adjustablerto the de-- siredrextent ziby selecting the: vcondenser dimen i "s'ionsoandz'also:the inductances in the circuitsproperly. 1:.-

Insteadzof recording the wattage the number of impulsemmaybe Erecordedif careis taken that the'rimpulseszvhavew all :.the t same duration andWattage; 5':

Theanodificatiomillustrated in Figure. 2:':ShOWS an aarrangementa inwhich the trigger: action; is

solely :obtairred by electromagnetic switches thus, 1.v

dispensingwith: the.x thyratronx:

beenzbuiltriipandtcl'os'es the circuit 41 containing a sourcemfcurrent148 'andzthe relayswitch 50.-

The zlatterzcloses thefheating circuit 25 containingrthewresistancel5,.".a sourceof current 32 and thezrecording meterr30 which inthis'casemustbe r"- a wattmeter; c."

The modifications described, as above stated;

arezdesignedior difierent'degreesof precision;

All theimodifications shownhowever, embody the principletousefthermocouples generating op-' posing r currents and kept at the sametempera-' tore-at one 'endy one of saidcouples 'being acted -may be readon or recorded by a suitable" meter or counter; if impulseeofa knownwattage are de- I liveredp is directly-proportional to the pharosage(radiant power per square unityo'r to the phosage (radiant energy persquare-unit) determining the temperaturer rise :in the radiationreceiving r;

thermocouple. 5 As :the -instrument is completely 7 automatimit'mayoperate"either with.or without" i anioperator.

Onf account-of the automatic operation'the in-' strument maybe 'iusedfor' meterological and for. radiation measurementsconnected withall-kinds of radiationy 'but'rit may also be used for indus' trialpurposes as alpyrometer in those cases where great accuracy is requiredor for the purpose of "measuringor controlling anillumination orirradiation automatically. I

Further applications willsuggest themselves'to the expertskilled inthisart. M It is to beunderstood that while the instrument h'as beendescribed astaninstrumentforfl-m measuring; the spharosage: (power :per.unit area) 4 or tor the tmeasurementr of :phosage ,(energy perunitareal-it may also be adapted for the measure-v I ments of other.units.

tionm Inithis: modificationtwo successive steps .to switchsin.thetheatingscurrenttare;used; The first switch formed by the relayswitchingdevice 46 r whieh roperates'zas soon as a'sufficientvoltage has4:

Having described the invention, what is claimed as new is: e

1. An integrating radiation measuring instrument comprising a pair ofthermocouples with joined ends connected for generating currents ofopposite sign, one thermocouple being exposed at the fused ends to theradiation to be measured, the other couple of the pair being heatable atthe fused end by locally produced heat, the joined ends being exposed tothe same constant temperature, the thermo-currents, when the fused endsare at the same temperature, neutralizing each other, while adifferential voltage appears across the joined ends of the thermocoupleswhen the fused ends of the thermocouples are unequally heated, anelectric heater adapted to produce the heat for influencing thethermocouple exposed to locally produced heat, a source of heatingcurrents, a heater circuit for connecting said heater and said source ofcurrent, an intermittently operative electronic tube with a grid, thegrid bias voltage of which controls the conductivity and the flow ofcurrent through said tube, an operative circuit for said electronictube, including a plate circuit, means in said plate circuit forcontrolling the circuit connecting the heater with the source ofcurrents, means said aforesaid heater circuit for producing short timedimpulses in the same, when the electronic tube is conductive, said meansincluding a relay in the heater circuit controlling the operativecircuit of the electronic tube, means for controlling the grid bias ofthe grid of the electronic tube by the differential voltage of thethermo-currents appearing between the joined ends of the thermocouples,the addition of a differential voltage to the grid bias making theelectronic tube conductive, the means in said plate circuit beingoperative to close the said heater circuit when the electronic tube isconductive said circuit being again broken upon energization of theheater circuit, and this pulse producing making and breaking continuingas long as the electronic tube is conductive, and an integrating meterfor measuring the integrated electric power delivered by the currentimpulses to the electric heater during the time during which the circuitwas closed.

2. An integrating radiation measuring instrument comprising a pair ofthermocouples with joined ends connected for generating currents ofopposite sign, one thermocouple being exposed at the fused ends to theradiation to be measured and the fused end of the other thermocouplebeing heatable by locally produced heat, the joined ends being held atthe same constant temperature, the thermo-currents of the two couplesneutralizing each other when the temperatures of the fused ends areequal, while a differential voltage appears between the two joined endsin the event of a temperature difference between the fused ends of thethermocouples, an electric heater adapted to produce the heat which theheatable thermocouple receives, a local source of currents supplying aheating current, a heater circuit connected with said source, a relayswitch for controlling said heater current, means for limiting thesupply of heating current to the electric heater to the value necessaryfor heat ing the thermocouple exposed to local heat to the sametemperature to which the thermocouple exposed to radiation Was heated,said means including a voltage responsive further relay switchcontrolling the operation of the first named relay switch, said furtherrelay switch being operated by the differential voltage of thethermocurrents appearing at the joined ends of the two thermocouples,said switch when operated maintaining the first named relay switchclosed as long as the differential voltage has a value different fromnil, the first named relay switch being opened when the diiferentialvoltage is equal to nil, and a meter for measuring the total heatingcurrent consumption of the heater, heating the locally heatedthermocouple.

3. An integrating radiation measuring instrument comprising twothermocouples, each having fused ends and a pair of open ends with theopen ends of the thermocouples being joined so that currents generatedby the fused ends oppose each other, the fused ends of one of the joinedthermocouples of the pair being exposed to the radiation to be measuredand the fused ends of the other thermocouple of the pair being heatableby locally produced heat, the joined ends of both thermocouples beingheld at a constant temperature, an electric heater for producing saidlocally produced heat to be transmitted to the last named thermocouple,a heating circuit and a source of electrical energy for energizing saidheating circuit, means responsive to a difference in potential betweenthe joined ends to energize the heating circuit when such difference inpotential exists to bring the heatable thermocouple, heated by theelectric heater, to a temperature at which it generates currents of thesame magnitude and of opposite sign to those produced in thethermocouple whose fused ends are exposed to radiation, said last namedmeans including means operated by the differential voltage developed atthe joined end of the pair of thermocouples for making and breaking thesaid heating circuit, and for definitely de-energizing said heatingcircuit when the differential current at the joined ends of thethermocouples disappears, and an integrating meter in said heatingcircuit measuring the total electrical energy locally furnished to theelectric heater.

4. An integrating radiation measuring instrument comprising a pair ofthermocouples joined at their ends and generating currents of oppositesign at these joined ends, the fused end of one of said thermocouples ofthe pair being exposed to the radiation to be measured, the fused end ofthe other thermocouple of the joined pair being heatable by locallyproduced heat, and the joined ends of the pair being held at the sameconstant temperature, an electric heater, a heating circuit forproducing heat in the electrical heater, the heat produced in the heaterbeing transmitted to the fused end of the heatable thermocouple of thepair, the pair of thermocouples when their fused ends are exposed to thesame temperature producing currents neutralizing each other and whenexposed to difierent temperatures generating a differential current attheir joined ends, means connected with said joined ends of the pair forcontrolling the heating of the electric heater, said last named meansincluding means operated by the production of a diiferential voltage atthe joined ends of the pair of thermocouples for making and breaking theheater circuit continuously so as to produce a series of present pulsestransmitted to the electrical heater, said means operated by thedifferential voltage generated at the joined ends of the thermocouplesclosing said heating circuit after each electrical current pulse duringthe production of a differential voltage at the joined ends of thethermocouples, but maintaining the heating circuit in open conditionwhen the differential voltage disappears thus automatically cutting offthe supply of further electrical energy upon reaching a state ofneutralization of the thermo-currents of the pair, and an integratingmeter in said heating circuit measuring the total electrical energylocally produced and supplied to said heater.

5. An integrating radiation measuring instrument comprising a pair ofthermocouples joined at their ends to generate currents of opposite signproducing a differential voltage if said currents are unequal, the fusedend of one of the thermocouples thus joined being exposed to theradiation to be measured and the other thermocouple being heatable bylocally produced heat, the joined ends of the pair being kept at thesame constant temperature, an electric heater adapted to produce heatfor influencing the last named thermocouple, a source of heating currentand a heating circuit connecting said heater and said source of current,circuit interrupting impulse producing means in said heating circuit,adapted to supply short timed pulses delivered at predeterminedintervals to said heater, voltage responsive means connected with thejoined ends of the pair of thermocouples, said voltage responsive meansbeing controlled by the difierential voltage produced at the joined endsif the pair of the thermocouples are heated unequally, said voltageresponsive means operating the said circuit making and breaking means inthe heating circuit and closing the said circuit after each breaking ofthe circuit during the existence of a differential voltage, whileopening the said circuit definitively upon disappearance of adifierential voltage, and an integrating meter for measuring the totalelectric power of the current impulses delivered to the electric heater.

6. An integrating radiation measuring instrument comprising a pair ofthermocouples joined at their open ends and connected to generatecurrents of opposite sign, the fused end of one thermocouple of the pairbeing exposed to the radiation to be measured, and the fused end of theother thermocouple of the pair being heatable by locally produced heat,the joined ends of the pair being kept at a common constant temperatureand the thermo-currents produced in the pair neutralizing each otherwhen the fused ends of the thermocouples are at an equal tempera.- ture,a difierential voltage appearing when the temperatures are unequal, anelectric heater adapted to produce the locally produced heat for thelast named thermocouple, a source of heating currents, a heating circuitfor connecting said heater and said source of currents, anintermittently operative electronic tube with a grid, the grid biasvoltage of which controls the conductivity and the flow of currentthrough said tube, an operative circuit for said electronic tube,including a plate circuit, means in said plate circuit for controllingthe heating circuit, the grid bias of the grid of the electronic tubebeing controlled by the differential voltage of the thermo-currentsproduced by the pair of joined thermocouples, so that the electronictube is conductive upon appearance of a differential voltage andnon-conductive upon disappearance of a differential voltage, means forautomatically interrupting the operative circuit of the electronic tubeafter its energization, the heating circuit control means in said platecircuit being operative to keep the said heating circuit closed when theelectronic tube is conductive and to break it upon cut off of the tubecircuit due to disappearance of a difierential voltage, and a meter formeasuring the total current consumption of the electric heater duringthe time during which the heating circuit was closed.

'7. In an integrating measuring instrument as claimed in claim 6 inaddition, an impulse producing relay inserted in the heater circuit,said impulse relay controlling the current flow in the operative circuitof the electronic tube so as to operate the same intermittently.

8. An integrating radiation measuring instrument comprising a pair ofthermocouples joined at their ends and connected to produce currents ofopposite sign, one thermocouple of the pair being exposed at the fusedend to the radiation to be measured and the other thermocouple of thepair being heatable by locally produced heat, the joined ends of thepair being kept at the same constant temperature, the thermo-currents ofthe pair neutralizing each other when the fused ends of boththermocouples are at the same temperature, while a difierential voltageappears .across the joined ends when the temperatures at the fused endsare unequal, an electric heater adapted to produce heat for influencingthe last named thermocouple, an intermittently operated electronic tubeprovided with a cathode and anode and with a grid, the grid bias voltageof which controls the conductivity of the tube, said grid beingconnected with the joined ends of the pair of thermocouples and theappearance of a difierential voltage producing a grid bias making thetube conductive, an operative circuit for said electronic tube includinga plate circuit, a source of currents, a condenser connected across theelectronic tube in said operative circuit of the electronic tube, aheater circuit connecting both sides of the said condenser with theelectric heater to provide the heater with the heating current upondischarge of the condenser, a relay in the plate circuit of theelectronic tube controlled by the flow of current through the said tube,and controlling the connection of the heater circuit with saidcondenser, said relay thus producing heating impulses and beingoperative to close the condenser discharge and heater circuit when theelectronic tube is conductive, while breaking the heater circuit upondisappearance of a differential voltage producing a grid bias making thetube conductive, and an integrating meter for measuring the total sum ofthe electric power of the current impulses delivered to the electricheater during the time during which the circuit Was closed.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,863,373 Harrison June 14, 1932 2,113,928 Behr Apr. 12, 19382,169,101 La Pierre Aug. 8, 1939 2,305,396 Volochine Dec. 15, 19422,349,436 Keeler May 23, 1944 2,398,606 Wang Apr. 16, 1946 2,556,841Farnell June 12, 1951

